Prior known methods for synthesizing the aforesaid aminosugars include, for example, (1) those which use sugars as starting materials [see, for example, Topics in Antibiotic Chemistry, Ellis Horwood, Ltd., Chichester, Vol. 2, pages 137-155 and Chem. Comm., 973 (1976)]; (2) those which comprise using petrochemical products as starting materials, subjecting them to stereoselective transformation to obtain the desired products as racemic mixtures [Angew. Chem, 90, 728 (1978) and Bull. Chem. Soc. Jpn., 52, 2731 (1979)]; and (3) those which use optically active naturally occurring materials other than sugars as starting materials [see, for example, Tetrahedron Letters, No. 40, pp. 3883-3886 (1979); ibid., 21, 2999 (1980); ibid., 22, 4017, 5073 (1981); and J. Chem. Soc. Chem. Comm., 442 (1980)]. The methods (1) are advantageous for obtaining optically active compounds because they start from sugars which already have a chiral center. But with these methods, the desired products cannot be obtained unless they go through long steps and therefore, these methods are economically disadvantageous. The key point of the methods (2) is the stereoselective transformation. But no decisive method is available for performing the stereoselective reaction, and another problem is that the final compounds should be optically resolved. At present, the methods (3) seem to be most advantageous for practical purposes. (+)Tartaric acid and D-threonine have been used as starting materials in the methods (3). But when tartaric acid is used as a starting material, the same defect as mentioned with regard to the methods (1) exists. Furthermore, D-threonine itself is not easy to synthesize because its synthesis requires a multiplicity of steps.